Electrical resistance



y 1937. D. 6. WILSON ELECTRICAL RESISTANCE Filed Oct. 18, 1954 Inventor: Dale G.Wilso T'1 Wan 115.4

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Patented M 6, 1931 UNITED STATES PATENT OFFICE 2,086,455 ELECTRICAL RESISTANCE New York Application October 18, i934, Serial No. 748,819

7 Claims.

My invention relates to electrical regulators and more particularly to improvements in resistance regulators of the liquid Contact type.

Heretofore electrical regulators of the liquid contact type have practically all consisted essentially of a variable resistance device comprising a resistor element which has variable amounts thereof short circuited by submerging it in a liquid conductor. Such regulators may be termed displacement type regulators, as the varying submergence of the resistor in the liquid displaces corresponding amounts of the liquid. As distinguished from this my regulator may be referred to as a surface-tension type regulator.

In accordance with one embodiment of my invention, I provide a resistor element with a relatively slidable electrical contact brush comprising a suitable liquid, such as mercury which is maintained in engagement with the resistor by means of the relatively high surface-tension and negative capillary attractionof the liquid.

By this constructional feature I have produced a regulator which is simpler, smaller and less expensive than displacement regulators of corresponding capacity.

An object of my invention is to produce a new and improved electrical regulator.

Another object of my invention is to provide a new and improved variable electrical resistance device.

Another object of my invention is to provide a new and improved electrical Contact.

A further object of my invention is to provide a variable electrical resistance device having a liquid surface-tension type Contact brush.

A still further object of my invention is to provide a novel automatic voltage regulator.

My invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

In the drawing, Fig. 1 is a sectional view of an operative embodiment of my invention; Fig. 2 is a perspective detailed view of a part of Fig. 1; Fig. 3 is a Circuit diagram illustrating an application of my invention to a voltage regulator for a two brush automobile battery charging generator; Fig. 4 is a modification of Fig. 3 in which the regulator is provided with an automatic current limit relay and Fig. 5 is a circuit diagram illustrating an application of my invention as a voltage regulator for a third brush automobile battery charging generator.

Referring now to the drawing, and more particularly to Fig. 1 thereof, I have shown my invention as enclosed in a casing I which may be made of any suitable material, such as punched and folded sheet metal. casing I, in a normally substantially vertical position, is a tubular member 2 which is supported within an insulating base member 3. The tubular member 2 is preferably, although not necessarily, cylindrical in shape and it is composed of nonmagnetic metal which is preferably of the type which is not affected by mercury. One such metal is that which is known in the art as Allegheny No. 88. Insulating base 3 may be composed of hard rubber or Bakelite; or the like. Set into the base 3.is a normally vertical resistor element 4 which is shown by way of example as a cylindrical resistance rod which is axially mounted with respect to the tube- 2. Resistor rod 6 may be made of any suitable material, such for example as the synthetic resistance material containing silicon and carbon and known to-the trade as Globar. The bottom end of the resistance rod 4 is preferably metal coated, such as by an iron spray, so as to facilitate making an electrical contact therewith. This metal coating is indicated at '5. Below the rod 6 and in contact with the metal coating 5 is a spacer or plug member 6 of suitable conducting metal to which is fastened a binding post I which is insulated from the casing i by suitable means.

Surrounding the upper part of the tube 2 is a solenoid operating magnet 8, which is normally wound of copper wire, and which has connected in series therewith a compensating resistance 9 having a temperature coefilclent of resistance opposite that of the copper so that the temperature coefficient. of resistance of the Circuit including the coil 8 and the resistance 9 is zero and is consequently independent of temperature.

This feature of compensating for the tempera-- ture ccefficient of resistance of a copper coil of a voltage regulator by means of an opposite characteristic resistance in series therewith is, however, an old feature and in and of itself, forms nopart of the present invention. One terminal of the coil 8 is connected to a suitable binding post, or terminal 10, which is insulated from the casing -l by suitable means and one terminal of the resistor 9 is connected to another similar binding post ll, whereby connections to the operating winding 8 of the regulator may be readily made.

Mounted within the tube 2 is a relatively loosely fitting steel plunger l2 having an integral bottom member I 3 provided with an opening therein which fits loosely around the resistance rod 4.

Mounted within the 2 aosasu As shown more clearly in Fig. 2, the bottom part of the plunger i2 is provided with a plurality of openings l4 in the form of curved slots.

Spaced within the plunger I2 is a small quantity of a suitable relatively high surface-tension electrical conducting liquid, such for example as mercury, which is indicated at l5. Due to the physical properties of this liquid it does not run out through the spaces between the bottom member l3 of the plunger, which serves to support the liquid, and the tube 2 and the rod 4 but on the contrary it is held inintimate contact with the tube 2 and the rod 4 by means of its surface tension. Consequently, this body of mercury I5 forms a ring-like or toroidal electrical brush acting as a bridging electrical contact between the tube 2 and the rod 4.

For making the other electrical connections to the variable resistance portion of my regulator I provide a binding post or terminal [6 which is fastened to a steel plug H which is in electrical contact with the tube 2.

If desired, a metal washer i8 may be inserted in the plunger [2 above the liquid I5 so as to maintain this liquid in place in the event of violent motion or shaking of the plunger l2.

In order to replenish any of the liquid l5 which may escape from the plunger I2 due to excessive vibration or violent motion of the plunger i2, or for any other cause, there is provided a reservoir ll of the same liquid in the bottom of the insulating cup 3. Thus with a sufliciently long downward stroke of the plunger l2 the supporting member 13 thereof will be submerged below the surface of the reservoir l9 whereby the liquid will enter the plunger through the spaces between the member l3 andtl'ie tube on the one hand and the rod 4 on the other. If desired, a ring-like washer member 20 may be provided on top of the reservoir I9 so as to prevent splashe ing of the liquid.

The'electric circuit through the variable resistance portion of my invention may be traced from the terminal It to the plug thence down the metal tube 2 to the outer surface of the mercury ring brush l5 then radially inward through the mercury IE to the resistance rod 4 and through this rod to the other terminal 1. with this circuit it will be seen that when the plunger is drawn up most of the resistance rod 4 is in the circuit while when the plunger is moved downwardly the length of the resistance rod 4 which is in the circuit is progressively shortened whereby the electrical resistance of the path through the regulator is correspondingly decreased. When the plunger is at the extreme bottom portion of its stroke the bodies l5 and I! of mercury merge thereby in eifect short circuiting the device and producing a negligible electrical resistance through the device.

. Due to the fact that my regulator is not a displacement type regulator the net weight of the plunger is a constant for all positions thereof except, of course, the extreme lowermost position when the bottom of the plunger is in the mercury I9. Due to this fact it isnecessary to have the range of motion of the plunger take place within the so-called uniform pull zone of the actuating magnet 8 in order that the device will operate satisfactorily as a regulator. By uniform pull zone is meant the zone wherein fora constant energization of the winding 8 the pull on plunger I2 is constant throughout a given range of positions. For an operating windber of layers of wire and for a plimger of cylindrical or tubular shape and of the same length as the operating solenoid this uniform pull zone will correspond approximately to a range of positions of the top ofthe plunger l2 from a position about four tenths of the way in the solenoid, from the bottom thereof, to a position about eight tenths of the way through the solenoid. However, it should be understood that I do not intend to be limited to any of these shapes or dimensions and that the plunger may be longer or shorter than the coil and that the thickness or other dimensions of the plunger shell may be varied or the core wound with variable depth of turns or any other expedient known in the art may be used in order to obtain a satisfactory pull curve which is accurate within the specified limits of regulation.

The natural air piston action between the plunger l2 and the tube 2 serves as a damping means for the regulator so as normally to prevent too violent movement of the plunger l2 and so as to adapt the regulator to the time constant of the field circuit of a generator which it may be used to regulate. It should be understood, however, that other methods of damping already known in the art may be used if found necessary.

Solenoid magnet 8 may be wound either for voltage regulator purposes or current regulator purposes, depending upon how it is intended to use the regulator. If the regulator is to be a voltage regulator the coil 8 will be wound with relatively high number of turns of relatively small wire so as to have a high resistance whereas if it is adapted for current regulations it will be wound with a few turns of relatively heavy low resistance wire so as to adapt it to carry the relatively heavy generator current.

In Fig. 3 I have shown my regulator connected for regulating the voltage of a variable speed two brush generator 2| having a shunt fleld winding 22.

Generator 2| may, by way of example, be a battery charging generator provided on an automobile and as shown it is connected, through a schematically represented conventional reverse current cutout 23, to a storage battery 24 and to load circuits comprising lamps 2i and a horn 26, the latter two being controlled respectively by switches 21 and 28. The terminals I. and II of the operating solenoid of the regulator are connected across the terminals of generator 2| and the resistor terminals I and Ii of the regu-.

lator are connected in series with the shunt field winding 22 of the generator. With this arrangement, any variation in speed of the generator 2|, normally tending to cause a change in its terminal voltage, will cause corresponding changes in the energiration of the winding 8 of the regulator, thereby causing the plunger II to move up or down, depending upon whether the voltage change was an increase or decrease, respectively, whereby the resistance in the shunt field circuit is increased or decreased, respectively, with the result that the voltage of the generator ismaintained at a substantially predetermined normal value, for as is well lmderstood by those skilled in the art, an increase in resistance in the field circuit of a dynamo-electric machine reduces the voltage thereof, while a decrease in the resistance of such a circuit tends to increase the voltage thereof.

Fig. 4 differs from Fig. 3 in that in the load circuit of the generator there is provided a current limit relay 2! having a it of normally 7;

mined safe value and as soon as this occurs and v the resistance 3| is short circuited the effect on .0 the regulator l is of a relatively large increase in voltage due to the fact that the short circuiting of the resistor 3i tends to increase the current ,ow through the winding 8. This causes the regulator plunger to pull up thereby insertingmaximum resistance in the circuit of field winding 22, whereby the voltage of generator 25 is reduced to a minimum value. This obviously reduces the current output of the generator .2! and as soon as the current output falls below the Z predetermined maximum safe value the relay 29 again opens its contacts 30. If overload conditions still exist on the load circuit of generator 2| the relay 29 will again close its contacts with the result that the relay 29 provides a definite vibratory type current limit for the generator 2!. With the arrangement shown in Fig. 4 the complete operation is such that up to the predetermined safe value current the voltage of the generator is maintained substantially constant, whereas as soon as the safe value of current is exceeded the voltage of the generator is dropped to its minimum value, whereby the maximum value current is definitely limited to a predetermined value.

Fig. 5 difiers from Fig. 3 only in that the regulator I is used for regulating the voltage of a third brush type generator 32. In such case, the terminals 1 and I6 are connected in circuit with the field winding of the generator 32 and the operating magnet terminals [0 and II are connected across the terminals of the generator 32. With this arrangement, the regulator regulates the generated current below the third brush setting and the third brush regulates the current to the value determined by the setting.

While I have shown and described a particular embodiment of my invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from my invention, and I, therefore, aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

'What I claim as new and desire to secure by said member and said material, a reservoir of said liquid at one end of said material, and means for moving said member along said material in order to vary the point of contact with said resistance, said motion havinga range sufiicient to submerge said support below the surface of said reservoir of liquid whereby any loss in said quantity of liquid .will be replenished.

2. In combination, a-pair of spaced substantially parallel vertical electrical conductors, a vertically movable member loosely fitted between said conductors, and a body of electrical conducting liquid carried by said member and engaging each of said conductors, said liquid having a surface-tension sufficiently high to prevent its fall ing through the spaces between said member and said conductors.

3. In combination, a metallic tube, a. rod of electrical resistance material substantially axially mounted within said tube, a movable circular supporting member loosely fitted between said rod and tube, and a quantity of relatively high surface-tension electrical conducting liquid carried by said supporting member and forming a ringlike electrical conductor between said rod and tube.

4. In combination, a pair of cylindrical electrical conductors arranged concentrically in spaced relation, a body of mercury, and means in spaced relation with said conductors for partially enclosing said'body of mercury between said conductors in such a manner as to maintain electrical contact between said conductors through said mercury.

5. In combination, a normally vertical metallic cylinder, a rod of electrical resistance material substantially axially mounted within said cylinder, a movable circular supporting member loosely fitted between said rod and cylinder, a quantity of relatively high surface-tension electrical conducting liquid carried by said supporting member and forming a ring-like electrical conductor between said rod and cylinder, and a reservoir of said liquid surrounding the bottom of said rod and adapted to receive said supporting member at the bottom limit of its range of motion.

6. In combination, a normally vertical tube of non-magnetic metal, an electromagnet winding surrounding the upper portion of said tube, a base of insulating material closing the bottom of said tube, a rod of electrical resistance material supported by said base and extending into said tube, a hollow solenoid plunger of magnetic material loosely fitted in said tube, said plunger having an opening in the bottom side thereof which fits loosely around said resistance rod, said plunger also having openings in its sidesnear the lower end thereof, and a quantity of mercury in the bottom of said plunger forming an electrical conducting path between said tube and said rod.

'7. In combination, a normally vertical tube of non-magnetic metal, an electromagnet winding surrounding the upper portion of said tube, a base of insulating material closing the bottom of said tube, a rod of electrical resistance material supported by said base and extending into said tube, a hollow solenoid plunger of magnetic material loosely fitted in said tube, said plunger having an opening in the bottom side thereof which fits loosely around said resistance rod, said plunger also having openings in its sides near the lower end thereof, a quantity of mercury in the bottom of said plunger forming an electrical conducting path between said tube and said rod, and a reservoir of mercury surrounding the bottom of said rod and adapted to receive said plunger.

DALE G. WILSON. 

